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Jaguar XK120 Review (1948 - 1954)

Overall Summary

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In 1940 Jaguar ceased production of their SS100, a stunning two-seater which boasted the looks that are still revered today among classic car lovers. World War II was not easy on the automotive industry and the famed British manufacturer had to wait 8 years before releasing a successor. The new sports car had a new name – Jaguar XK120 – after the SS was dropped due to the fact that those initials were carrying an unpopular burden of standing for one of the most hated Nazi divisions in history.

In 1948 the XK120 arrived carrying lots of the design ideas from the SS100, but also portraying significant attempts of modernization reflected in rounded shapes of almost everything. It was also a two-door sports car with a long hood and even further protruding headlights bordering the upright grille. The rear wheel was either hidden behind a fender skirt, or left wide open and the wavy trunk was only accompanied by two small, rounded lights and a lock.

There were three body styles to choose from: coupe, roadster and drophead coupe. The first one that appeared was the roadster, the first production model being bought by Clark Gable, with the coupe coming in 1951 and the drophead coupe in 1953. The three body styles are even today often referred to as OTS (open two-seater), FHC (fixed head coupe) and DHC (drophead coupe).

The FR layout was shared by all versions, as was the engine – the 3.4 l inline six-cylinder unit – although a 2 l four-cylinder was also planned, but subsequently dropped. The 3.4 had three generations, all of them with double overhead camshafts. The first one was produced for as long as the car itself, from 1948 – 1954. It provided the output of 160 hp at 5,000 rpm. It was joined by the 3.4 M (also called SE in Europe) in 1951 and it brought 20 hp more at 5,300 rpm. The same year saw the appearance of the most powerful engine the XK120 ever had – the 3.4 MC. It produced 210 hp at 5,750 rpm and had a different carburetor compared to the weaker two engines.

The XK120 was extremely successful as a racing car. In 1949 three XK120s entered the One-Hour Production Car Race in England. One of them had a flat tire and did not finish the race, but the other two managed to snatch the first two places. Some of the other wins include the Palm Beach Shores race, Pebble Beach Cup, Tourist Trophy (snatching the top three places), Alpine Rally (twice), Coupe des Alpes, Tulip Rally (the top two places), Mount Druitt 24 Hours Road Race and even the NASCAR road race, being the first import car to win this competition. In several other races, including the famed Le Mans, the XK120 was aiming for victories, but problems with clutch and brakes caused it to abandon the race in the 21 hour. These issues brought about a change in design that made the production model more reliable.

Similarly, the XK120 held numerous speed records. In 1949 it proved to be the fastest production car in the world reaching 132.596 mph with removed windscreen and sidescreens and added tonneau cover. And this was the 162 hp version of the car.

In 1950 it became the first production car to average the speed in the excess of 100 mph for 24 hours straight at the Autodrome de Montlhéry near Paris. The car covered more than 2,500 miles and had the average speed of 107.46 mph with the best lap averaging as high as 126.2 mph.

In 1951 it was driven for 131.83 miles in one hour at the same track with the thrilled driver Leslie Johnson explaining that he felt the car could go that way for a week. What might have seemed like an exaggerative remark was put to test a year later and the FHC XK120 was actually driven for a full week. Even though it broke a spring during the exhausting test, the car broke numerous records on that run (Class C 72-hour, four-day, 10,000 km, 15,000 km and 10,000 mi), including the full seven days, each of them averaging at more than 100 mph. A true display of dominance by the XK120. The engine was so advanced that the basic design was still used well into the 1980s.

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Driving & Performance

The first cars were made of aluminum, while the latter ones were significantly heavier, being made of steel, but also notably more powerful. Also, there were two compression ratios used – 8:1 and 7:1 for the UK market due to the 70-octane fuel used in the UK at the time. However, all of the versions were magnificent to drive and vast majority of the records and race victories mentioned above was achieved using regular production road-going cars – they were just that good.

The top speed was measured several times for different versions and it ranged from 124 mph to well over 130 mph. The acceleration to 60 mph was at around 10 seconds.

In terms of cornering performance, the XK120’s suspension was a work of art at the time. The front was reserved for independent torsion bar, while the rear had semi-elliptic leaf springs. The XK120s were also fitted with recirculating ball steering.

The biggest issue with all XK120s was their brakes. The 12-inch drums had sufficient stopping power but fading was an issue, especially having in mind the speeds they were dealing with and this was especially evident in the early years of racing. The issue was somewhat resolved when certain models received Alfin aluminum drums.

The M version was more race oriented and it boasted more power, dual exhaust and firm suspension which was more suitable for high-speed cornering.

Driving an XK120 was a thrill. The fastest production car of its time is enough of a reputation, but there was more. The entire car, with the exception of the standard brakes, was engineered to support such outstanding performance. The inline six engines are known to be extremely well balanced and dual overhead camshafts only helped as well. The transmission was precise and easy to manipulate and the heavy front made the car sway gracefully while turning, carefully obeying the steering wheel.

Equipment & Comfort

Even though the XK120 was the fastest car of its time, amazing attention to detail within production is what made it incredibly popular among high-class customers. Standard leather seats were remarkably long and comfortable. They resembled bench-like seats on far larger American cars. There was an option of choosing more rounded seats which provided amazing lateral support much like sports seats of today. The support was far greater than that of some faster and younger Porsche models,

The handbrake was on the left for both LHD and RHD cars. The most notable interior feature was the centered dashboard. On each side there were two large dials serving as a rev counter and speedometer. Between the two, there were several smaller dials and knobs and all of the car’s features were controlled from here.

The roadster was considered the base model. For this reason the DHC and FHC were far more luxurious, so they often featured wood on the dashboard and door-caps. However, the roadster was not cheap either, boasting high-quality leather instead of wood.

The mentioned removable fender skirts were unavailable for cars produced from 1951 which featured wire wheels. Another peculiar exterior feature was the lack of door handles. The canvas top for the roadster, sidescreens, windscreen and aeroscreens could all be removed and exchanged for one another and they could all be put away very practically behind the seats.

Running Costs

The XK120 was a high-class car that brought Jaguar to the big league. Parts are not considered cheap. The easiest breaking part are the brakes which are known to fade during heavier use and a brake drum will set you back for about $260. However, if you really want the ultimate, there are aftermarket disc brake kits for the XK120 which may cost more than $2,000.

An entire clutch kit costs about $300 and an alloy flywheel can be found for a bit more. A rear leaf spring costs about $300 as well.

However, the XK120 is considered a very reliable car and, when in good condition, it shouldn’t cause any major problems. It was constantly improved over time as issues were emerging during races. Using a road car as a racing machine means that it has to be very heavy duty and if racing was no problem for it, daily cruising will see the parts last forever.

History & Development

The first XK120 saw the light of day in 1948 at the London Motor Show. It was a roadster and the first car with the XK engine. The first 242 XK120s had aluminum bodies, but just one year into the production they changed to steel ones to keep up with the demand, thus increasing weight by 112 lb.

The first XK120 models featured a 3.4 l I6 engine that produced 160 hp and they were the least powerful ones, but they were more than sufficient to set the new record for the fastest production car in the world. The number 120 in the name stood for the presumed top speed, but the fastest early model actually reached 135 mph with slight alterations which made it more aerodynamic. The alterations were all available for road cars and they included simple things like a tonneau cover and replacing the windscreen with one aeroscreen.

This engine was available throughout the production timeline and the basic design was kept for the more powerful versions as well. In 1951 it was joined by two more engines. All of them shared the same bore and stroke and the first two shared the double SU H6 carburetors, with the newer one boasting 20 hp more, while the most powerful one provided 210 hp using double SU H8 carburetor. All of the versions featured a very advanced DOHC design with hemispherical chambers and inclined valves.

Not many things changed throughout the years the XK120 was produced. Most of the changes occurred when heavy-duty racing proved that a part needed an improvement.The changes usually meant that the part was made more rugged, rather than technologically different due to the fact that the XK120’s components were pretty much state of the art at the time.

The XK120 was replaced by the Jaguar XK140 in 1954, which was more of an improved and modernized XK120 than a whole new model.